466 J. M. D. OLMSTED 



the taste-bud indicates the time at which the nerve supplying it 

 reaches the surface needs verification for taste-buds in Amiurus." 



There are two cases in which it seems to have been proved that 

 differentiation of sense organs is dependent upon the nerve, 

 namely, the formation of the tactile corpuscles of Merkel (Szy- 

 monowicz, '95) and of Grandry's and Herbst's corpuscles (Szy- 

 monowicz, '96). 



The growth of such organs as teeth, however, is claimed to be 

 absolutely independent of the nervous system (Moral and Hose- 

 man, '19). But the nerve does exert a regulating influence, 

 either increasing or decreasing the rate of growth, or causing 

 changes in color of the tooth. 



In another paper (to appear shortly) I have described the de- 

 generation of taste-buds which occurs after severing the branches 

 of the seventh cranial nerve leading to the barbels of the catfish, 

 Amiurus nebulosus, and also the reappearance of taste-buds di- 

 rectly attendant upon the regeneration of the nerve. The present 

 paper affords additional evidence that the presence of the nerve 

 is the formative influence in the development of taste-buds. 



MATERIALS AND METHODS 



When the end of a barbel (0.5 to 1 cm.) of Amiurus is cut off, 

 sufficient regeneration takes place under normal circumstances to 

 become evident to the eye at the end of two weeks. The regen- 

 erated portion appears as a colorless finger-like projection, having 

 less than half the diameter of the stump from which it springs. 

 "When prepared withMallory's phosphotungstic haematoxylin, ac- 

 cording to the directions given on page 369 of Mallory and 

 Wright's " Pathological Technique," the cartilage, pigment cells, 

 and connective tissue stain a brilliant red ; the nuclei of epidermal 

 cells and of the nervous tissue stain a brilliant blue; while the 

 nerve fibrils and cytoplasm of the epidermis, especially the cyto- 

 plasm of the sense cells of the taste-buds, take on a characteristic 

 lilac hue. 



RESULTS 



Such preparations show that regeneration is more rapid in the 

 region near the old stump of cartilage. It is rapid growth in this 

 region that causes the finger-like appearance of the new part. 



